1. Field of the Invention
The present invention relates to an ink jet recording apparatus including an ink absorber for retrieving or retaining waste ink that is not used in image recording.
2. Description of the Related Art
Many recording apparatuses that form (record) an image on a recording medium such as recording paper on the basis of image information are used as photocopiers, facsimiles, and printers. The recording apparatuses employ various recording technologies. Among them, an ink jet recording technology is a low-noise and non-impact recording technology. In the ink jet recording technology, ink is discharged from discharge ports of a recording head serving as a recording device, and recording is thereby performed. In the ink jet recording technology, ink is directly attached to a recording medium such as paper, cloth, non-woven cloth, or an OHP sheet. Ink jet recording apparatuses employing such a recording technology have the advantage that a high-density and high-speed recording operation can be performed.
Generally, ink jet recording apparatuses are configured to discharge ink droplets from minute discharge ports formed in a recording head, to attach the ink droplets to a recording medium, and thereby to perform dot recording. Therefore, bubbles and dust can enter the discharge ports, and ink can be thickened due to evaporation of ink solvent. Such can cause defective discharge of ink and can thereby deteriorate image quality. In order to eliminate these causes of defective discharge, a discharge recovery process is performed. In the process, the ink in the recording head is refreshed, and normal ink-discharging function is thereby maintained or recovered.
As a form of this recovery device (or recovery unit) that performs discharge recovery process, there is a recovery device including a cap and a pump. The cap is capable of covering a discharge port surface of a recording head in which discharge ports are formed. The pump communicates with the cap and exerts a sucking force. The recovery device exerts the sucking force in a capping state, i.e., with the cap attached to the discharge port surface, thereby forcibly discharging ink from the discharge ports. This process is called a suction recovery process. The recording device also performs ink discharge not effecting recording (preliminary discharge) with the cap or an ink receiver opposite the discharge port surface. This process is called a pressurization recovery process. These processes are for removing the causes of defective discharge such as bubbles and dust, together with ink. As disclosed in Japanese Patent Publication No. 63-61182, ink jet recording apparatuses generally have a waste ink absorber disposed in the apparatus body for accumulating waste ink produced in the discharge recovery process.
However, in ink jet recording apparatuses, the number of necessary recovery processes and the amount of ink discharged in each recovery process differ according to use, frequency of use, or product life of the apparatus. That is to say, ink jet recording apparatuses that discharge a large amount of ink in the recovery process require a capacious waste ink absorber, and such a waste ink absorber occupies a large space in the apparatus. On the other hand, ink jet recording apparatuses have been reduced in size, and various measures have been taken in order to secure a space for the waste ink absorber without increasing the size of the apparatus.
For example, U.S. Pat. No. 5,245,362 discloses a waste ink absorbing structure including a first absorbing member for containing waste ink, and a second absorbing member connected to the first absorbing member via a tube. When the amount of waste ink exceeds the capacity of the first absorbing member, the overflow is introduced into the second absorbing member. In addition, U.S. Pat. No. 5,172,140 discloses a recording apparatus having different waste ink absorbing members disposed in the spaces on either side of a recording sheet conveying section, which are normally empty spaces in the recording apparatus body.
Moreover, Japanese Patent Publication No. 7-57547 discloses a waste ink absorber having a multilayer structure including a plurality of ink absorbing members. This multilayer absorber can absorb and hold more waste ink than a single absorber of the same volume. The reason is that, due to the multilayer structure, interlayer gaps between the layers of absorbing members function as ink holding areas. In addition, in the multilayer waste ink absorber, the layers of absorbing members support each other. Therefore, the waste ink absorber is improved in resistance to collapse or compression due to its own weight, and unintended ink outflow from the waste ink absorber can be prevented.
However, the above known ink jet recording apparatuses including a waste ink absorber have the following problems. In the case of U.S. Pat. No. 5,245,362, the addition of connecting parts complicates the apparatus structure and increases the production cost.
In the case of U.S. Pat. No. 5,172,140, when the discharge recovery process is performed continuously and a large amount of waste ink is discharged at a time, the waste ink absorber can fail to absorb all of the waste ink. Therefore, at the worst, the waste ink can leak from the recording apparatus. The reason is that it takes a long time for the waste ink to spread from one absorbing member to another absorber.
In the case of Japanese Patent Publication No. 7-57547, indeed the absorption capacity can be increased, but since the interlayer spread of the waste ink is slow, ink absorption can fail to keep up with the ink discharge. Therefore, the waste ink absorber can fail to absorb all of the waste ink, and at the worst, the waste ink can leak from the recording apparatus.